In the prior art, it was known to use windmills with air compressor units that are powered by the wind energy turning the windmill, to store air under pressure for use, for example, in generating electricity. See for example U.S. Pat. Nos. 4,055,950; 4,236,083 and 4,447,738.
Windmill type designs have also been used in wind turbines with various shaped impeller blades and angles encased in a cowling designed to direct the wind over the blades. See for example U.S. Pat. Nos. 1,025,428; 4,021,135; 4,140,433; 4,132,499; 4,143,992; 4,324,985 and 4,720,640.
One of the primary goals of the prior art configurations was to get more revolutions per minute (rpm) out of the device. Thus, the blade configurations were such as to pass air quickly through the device. To do this, the blades would be so configured and positioned as to not interfere with each other's air flow.
One of the problems with prior art devices was that in sustained high winds they would tend to "run away" and burn up. Furthermore, at low winds or intermittent winds, they could not produce the sustained energy, i.e. constant speed, necessary to produce, for example, electricity.